In Japan, it is now estimated that the number of diabetic patients is about 6.9 million, and by including the persons of impaired glucose tolerance which can be called a prediabetic state, it reaches 13.7 million. Further, it is said that in one in ten of the national population older than the age of 40 are diabetic patients.
Diabetes is known to develop via impaired glucose tolerance which used to be called a borderline type. Accordingly, the progress towards diabetes can be inhibited by detecting this state as early as possible and treating the patient.
Conventional clinical diagnosis of impaired glucose tolerance and diabetes, is made by measuring a fasting blood sugar level and measuring the blood sugar level 1 hour and/or 2 hours after a 75 g oral glucose tolerance test. The fasting blood sugar level (hereinafter referred to as “FBS”) is used for screening because of its low load. According to the diagnostic criteria of Japan Diabetes Society, a level of less than 110 mg/dl is judged a normal type, 110 to 125 mg/dl, a borderline type, and 126 mg/dl or higher, a diabetic type. As the result of the above diagnosis, in a suspected case of diabetes, another 75 g oral glucose tolerance test is further conducted to make the final determination (with the blood sugar levels 2 hours after the glucose tolerance test, a level of less than 140 mg/dl is judged a normal type, 140 to 199 mg/dl, a borderline type, and 200 mg/ml or higher, a diabetic type).
However, the above determination method by means of FBS is not necessarily referred to as an accurate determination method because of the factors such as unstable type diabetes or contents of meal in the evening before the test. Further, the 75 g oral glucose tolerance test requires at least 2 hours and frequent blood sampling, and gives physical burden on patients, consequently that is not so favorable.
For detecting the prediabetic state or diabetic state, the following methods have been proposed for example.
(1) A method for detecting a prediabetic state by comparing the amount or increasing ratio of D-chiro-inositol in urine of mammal patients and that of healthy persons quantitatively determined in the same manner after a predetermined time, followed by the administration of sugar has passed (JP-A-2000-298131).
(2) A screening method for screening a mammal patient for the possibility of being diabetic using a urine sample from the patient, which comprises the steps of:1) keeping this sample in a bacteria-free environment, and 2) analyzing this sample about the presence of D-chiro-inositol; involving a step to define the absence of D-chiro-inositol, or the remarkably low level of D-chiro-inositol indicating no effect in vivo, as a state of being diabetic of the subject, wherein this low level is at least 3 orders lower than the level of non-diabetics (Japanese Patent No. 2,834,321).
(3) A method for detecting an insulin resistance in relation to the symptom of diabetes, wherein a chiro-inositol concentration as an index of the insulin resistance in relation to the symptom of diabetes in a urine sample or blood serum sample from mammal patients is measured (Japanese Patent No. 3,118,458).
(4) A method for screening a human for insulin resistance which comprises a step of measuring a concentration of D-chiro-inositol in body fluid, a step of measuring a concentration of myoinositol in body fluid, a step of calculating the ratio of myoinositol to D-chiro-inositol, and a step of comparing the ratio thus calculated with a ratio characteristic to the insulin resistance, wherein when the calculated ratio exceeds the ratio characteristic to the insulin resistance, this human is determined seemingly insulin resistive (Japanese International Publication No. 10-507826).
The above screening methods (1) to (4) are the methods for inspection which use urine and consequently require no blood sampling or the like, while urine sampling is needed within a predetermined time of period after glucose tolerance; for which the subject is placed under restraint for a predetermined time. From the above, these methods are inappropriate for general inspection. Further, they have a problem of being so complicated that it is impossible to treat a lot of test specimens.